Health knowledge made personal
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I still marvel at the accomplishments of CAT scans and imaging studies. These technologies have revolutionized the medical profession. Imagine foretelling 50 years ago that a new technology would emerge that could perform ‘exploratory surgery’ without an incision. This prediction would be greeted with disbelief, if not scoffing. Of course, there would be similar reactions if decades ago other technological feats, such as fax machines, personal computers, emails and internet, were predicted. CAT scans save patients’ lives, prevent surgeries, make accurate diagnoses and refine treatment plans. This is the good news. However, as expressed repeatedly on this blog, there is a darker side of the story.
Recently, the press went ga ga over a new study that concluded that screening CAT scans on cigarette smokers could save lives. They hyped headline of The New York Times was CT Scans Cut Lung Cancer Deaths. The study concluded that annual chest CAT scans on smokers could reduce the risk of death by lung cancer by 20%. Why is my reaction so cynical to what was heralded a groundbreaking development in oncology? First, I am always wary when study results are presented in relative terms, such as a 20% decrease in the number of deaths. Relative percentage terms always exaggerate the clinical benefits and are misunderstood by the public, as well as the press. For example, assume that a new cholesterol-lowering medication is prescribed to 500 people who are compared with a control group of untreated individuals to determine if the drug can prevent heart attacks. If 4 folks in the medication group develop a heart attack, and 5 control patients do also, then the drug company can correctly claim it lowers heart attack rates by 20%. This sounds impressive, although the true benefit that an individual realizes is trivial, since 99% of all patients suffered no cardiac event. Can’t you just see the headline Drug Cuts Heart Attack Rate by 20%?In the chest CAT scan study, 300 people must be screened to save one life. Is this worth it? Of course, if the lucky individual is in your family or mine, then any cost would justify the outcome. However, we cannot make public policy based on anecdotes or rare favorable outcomes. For those who argue that saving lives is worth enormous expense at the expense of others, do they also support the following positions which would save lives?
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